Safety device for motion picture projecting machines



Aug. 4, 1931.

J. F. ADAMS ET AL SAFETY DEVICE FOR MOTION PICTURE PROJECTING .Filed Oct. 31, 1927 MACHINES 3 Sheets-Sheet l INVENTORS: 1571 12 Francis/Mame 5 mdsfYI/lllen BY 2 ATTORNEY.

8 4, 1931- J. F'. ADAMS ET AL 1,317,661

SAFETY DEVICE FOR MOTION PICTURE PROJECTING MACHINES Filed Oct. 31, 1927 3 Sheets-Sheet 3 TIC-71.5

WJTNES 5E5.- INVENTORS:

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Patented Aug. 4, 1931 1 fenn sra'rss ATE T caries JOiiNirRANO 'sY nAMs ANDTHOMAs T. ALLEN, F PHILADELPHIA, PENNSYLVANIA, AssIeN R's To SENTRY SAFETY CONTROL CORPORATION, OP PHZLAD'ELPHIA, PENN- fsYI veNm, A 'coRPeim'rIoN or DELAWARE 'sAFE'r Y DEV OE' F R MOTION PICTURE PROJsoPINe MACHINES (pi; -x-" I I mvellfilon relates to automatic control apparatus for motion picture projecting machines: and more particularly to a safety device'adapted to form the main unit ofsuch apparatus. D ;One, of the most prolific sources of fire 1n motiori picturetheaters is the ignition of the film, :whichTis-causedby itsfailure to move withfsutlicientrapiditythrough the rays of lightffrointhe lamp .or by breaking and comin contactwith the lamp housing. If the filmv fails .to move through the pro ect1ng machine at or abovera certain rate of speed, the imagesare not projected upon the screen with sufficient rapidity to produce the illu- I sion of continuous movement and oftentimes a decided flicker in the picture results.

Qne objectof-our invention is to provide a safetyzdevice adapted to. intercept the rays of light passing through the film and stop the projecting mechanism whenever any incident qr accident occurs which would tend to faulty projection or produce a fire hazard.

. Another object of our invention is to proza vide a device which is compactlybuilt and so simple. in construction that there is little likelihood of its getting out of order.

Still another object of our invention is to provide a device of this character having fewparts and which may be economically manufactured and installed.

, According-to the invention, the safety device comprises a casing having a shaft upon which a dowser is fixedly mounted, means on the shaft cooperating with tripping means for holding the dowser out of light obstructing position,'an electromagnet and an armature for said magnet hingedly mounted thereon and adapted to be drawn to the electric magnet when it is energized, and means normally urging said armature away from said magnet and which, when the magnet is deenergized, will operate the tripping means to release the dowser and permit it to fall into light obstructing position. The casing isalso provided with a switch which is located in the motor circuit and the shaft is provided with means which will open this switch when the dowser falls.

The drawings illustrate an embodiment Application-filed October 31, 1927. Serial No. 230,062.

of the invention and the views therein are as follows:

Figure 1 is a rear elevation ofa safety device embodying our invention; the rear cover of the casing being omitted and certain parts broken away.

Figure 2 is a side view lookingfrom the right of Figure 1 but showing the casing cover in place; the casing and cover being shown in section and the other parts in full and certain parts broken away.

' Figure 3 is a view looking fromthe left of Figure l but showing the casing'cover in place and the greater part of the casing broken open to its center line.

Figure 4 is a detail plan view of a magnet armature, andv v 1 1 Figure 5 a wiring diagram showing the relation of. our improved. safety device to other elements forming an automaticcontrol apparatus.

. Referring now more in detail to the drawings, the device is shown as being provided with a casing 10 having a base 11 adapted to be secured upon the cone 12 of a motion picture projecting machine and adapted to fit various sizes of cones by means of fillers 13 disposed between base 11 and cone 12.

.The rear side of casing 10 is closed by a cover 14 preferably provided with an insulating lining 15. A shaft 16 is journaled in the front of casing 10 and in cover 14: and has a dowser fixed on its outer end which consists of a dowser handle 17 and a dowser plate 18.

A latch 19, rockablymountedin the bifurcated end of dowser handle 17, is adapted to be held between a stop 20 and a shoulder 21 when dowser plate 18 is positioned over the opening of cone 12. When dowser plate 18 falls, latch 19 will ride up the sloping face of shoulder 21, strike stop 20 and be drawn downwardly therebetiveen by a spring 22 having one end secured to latch 19' and its other end secured to dowser handle 17, thus preventing dowser plate 18 from oscillating and rigidly looking it in light Obstructing position. To remove dowser plate 18 from light obstructing position, the operator depresses the hand grip 23 of latch 19, so as to raise the end of latch 19 above shoulder 21, and swings dowser plate upwardly until dowser handle 17 strikes a stop 24 secured in the front wall of casing 10.

A tri ger" 26 is rockably mounted ideasing 10 many suitable manner, as by means of a screw 27 passin through trigger 26 and threaded into Front-wall of casing 10, and extends through-ca suitable opening in the side wall of casing 10 so that it may-being'collar 28 and shaft '16 to rotate and dowsewplat 18 1-16; i falll When raising dows'er plate 18 after trigger 26' has been released, roller '31l1 willrideon the periphery of collar28iintil it can 'enter'qnotch 29 and hold'the dowser in raised position.

- A non-conductingswitchbase 32,"secure d in the bottom portion of' ca'sing 10, carries a spring contact 33-011 one of its ends anda fixed contact 34 on its other end; suitable 'contact points 35 'being preferably fined to the meet: ing'ends of the ontac't'slif Abarn 36,,prefe rably made of insulating material, is fixed on shaft 16 immediately above spring contact 33 and is adaptedto sp'ring this conta'et away from fixed contact 34whe'n shaft '16 is rotated by the falling of dowser'plate 18. An insulating bushing 37 1s preferably disposed on shaft 16 'between"cam"36 and collar 28 and an insulating bushing 38 disposed between cam 36 and'lining 15'of the casing cover; In order that there may be no possible chance of short circuits or leakage of current between contact 33 and shaft 16, the joints between the ends of bushings 37 and 38 and'the sides of cam 36 are filled with cement 39. d

An electromagnet 41. has been shown se cured in casing 10 by providing a cradle 42, having a flat face tofabut the frontwall of casing 1 0 and a concave face adaptedto par tiallyencir'cle magnet 41', andpassing screws 43 through the casingand cradle and into the shell of the magnet which, in the device illustrated, is made of metal. v A magnet armature 44 is adapted to rest on the top of the casing of magnet 41 and is provided with a slot 45 and an aperture 46. An armature stop- 47 is fixed to the side of the casing of magnet 41 and has an upwardly extending part of reduced width which passes through the slot 45 and is bent over armature 44. A hook 48 is formed on the lower end of armature stop 47 and supports the lower end of a coil spring 49 whose upper end is secured to a bolt 50 which passes through aperture 46 and is held against downward movement by a nut 51. Magnet 41 is adapted to hold armature 44 against the upper end ofits shell "against the action "of spring 49 until it is deenergized when spring 49 will vtilt armature44 upwardly against stop -Nut 51 is reduced in thickness for the greater part of its area so as to, leave aprojection 52 adapted to overhang the ehd of armature 44. vgTo adjust its tension, spring 49 is stretched so that nut 51 may be moved in'the'desired direction on screw 50, the

spring released and nut 51 turned. so that projection 52 overhangs theend offarniature 44 and locks it against rotation; the tension of'spring 49 should be such that it is capable of holding armature 44 agaiiist'st'op 47 magnet 41 is deenergized. I

' "Ajtrip 54'has oneefid' ecaredtp ,arniature 44 and a fork 55 securedjto'or farmed nearits other end and-adapted to straddleitrigger The lower end of trip :54 is bent inwardly and supports a weight 56 whicliiis adapted" toadd i impetus to the movement-of the trip 54, when magnet 41 is deenergizedf and the armature swung upwardly-by spring 49, so as to strike a blow against the underside of trigger 26.

The device isshown in Figure 1 inthe po- 'sition occupied when the projecting'inachine is inoperation ,magnet 41' being energized its core slightly'spaced fromarriiature 44. When magnet41'is de'energi z ed, as will be hereinafter described; spring 49 is'wings armature upwardly"and" consequently swings fork 55 against trigger 26. Weight 5 being secured temp 54, it"wi11be swung upwardly by the-action of spring 49 ahdthe energy required toovercome'its inertia posi-' tively assures, the raising of triggerf26f j Referring now to Figure 5, we haveshowi'i the motor M, which drives the projecting machine, and the automatic control apps; ratus as deriving their power from a-fpower line AB through a'swit'ch60 which has oiie of its holes connected to one side of motor M through a wire 61 and its other pole connected to one, pole of a relay' switch' 62' by a wire 63; the other pole of relay 62fbeing connected to the other side of motor M by a wire 64." One end of the winding 65 0f re lay 62 is connected to wire '63 and its other end is connected to contact 34 by a wire 66.

' A centrifugal switch67 which opens when the projecting mechanism has attained a certain speed, and film actuated switches 68 and 69, which are open when the projecting n1a-' chine is in operation, are diagrammatically represented and shown 'as having one pole of each connected to wire 61*by'af'wire70 and the other pole of eachconn'ected to "one end of the winding of magnet '41 by a wire 71, thus putting theseswitch es 'infpar'allel with one another.

The other end of the winding of magnet 41 is connected to contact 34 by a wire 72 and contact 33 is connected to wire 70 by a wire 73. A resistance 74 has one side connected to wire 64 and its other side connected to wire 71 by a wire 75.

Assuming that switches 68 and 69 are open and the other switches closed, current may (low from switch 60 through wire 61, motor M, wire 64, relay 62, and wire 63, thus providing energy for the motor. At the same I time, current may flow from wire 61 through any other condition arise which would cause it to move substantially out of its normal path, one or both of switches 68 and 69 would be closed. If the film should slow down from any cause, such as unsufficicnt power to the motor or trouble in the motor or projecting mechanism, switch 67 would close. When one of these switches close, current may flow from wire 70 through the closed switch to wire and thus momentarily deprive magnet 41 of a portion of its power and deenergize same sufliciently to allow spring 49 to swing armature 44 upwardly and cause trip 54 to raise trigger 26 and release the dowser. WVhen the dowser falls, dowser plate 18 obstructs the light passing through the film and cam 36 separates contact points 35, thus breaking the circuit at this point and deenergizing winding 65 which would cause relay 62 to open and stop the motor.

A safety device made as above described is simple and inexpensive to manufacture, it possesses no parts which would ordinarily get out of order, and it is positive in operation.

Of course, the safety device illustrated may be modified in various ways without departing from the invention herein set forth and hereafter claimed.

We claim 1. A safety device for motion picture projecting machines including a dowser, means including a notched disc engaged by a trigber for holding the dowser out of light obstructing position, an electromagnet, an armature hinged on the magnet, a trip secured to the armature and adapted to strike the dowser-holding means to release the same, electrical contacts, means associated with the dowser for separating the contacts when the dowser falls.

2. In a device of the character described having a dowser held out of light obstructing. position by a trigger, means for tripping the trigger including an electromagnet, an armature hinged on the magnet, a spring tending to tilt the armature, a trip secured to the. armature. and adapted to strike the trigger, and a weight secured to the free end of the trip to add impetus to the movement of the same. a

3. In a device ofthe character described having a dowser held out of light obstructing position by a trigger, means for tripping the trigger including an electromagnet, an armature hinged on the magnet, a trip secured to the armatureand adapted to engage the trigger, a spring secured to the magnet, and urging the same away from the magnet, a screw secured to the spring and extending through the armature, a nut on the screw, and a projection formed on the nut and overhanging the edge of the armature whereby the tension on the spring may be regulated and the nut prevented from accidental turning. i

4. Safety mechanismwfor motion picture projecting machines comprising a shaft, a dowser on theshaft, means on the shaft scooperating with a trigger for holding the dowser out of light obstructing position, an electromagnet, and anarmature for said magnet having a trip secured thereto, said armature normally held in engagement with the magnet by the energization thereof, but urged out of engagement therewith upon deenergizationof said magnet, whereby the trip strikes the trigger and releases the dowser to permit it to fall into light obstructing position.

5. Safety mechanism for motion picture projecting machines comprising a shaft, a dowser on the shaft, means on the shaft cooperating with a trigger for holding the dowser out of light obstructing position, an electromagnet, an armature for said magnet having a trip secured thereto, said armature normally held in engagement with the magnet by the energization thereof but urged out of engagement therewith, upon deenergization of said magnet, whereby the trip strikes the trigger and releases the dowser to permit it to fall into light obstructing position, electrical contacts for closing the motor circuit, and means on the shaft adapted to open the electrical contacts when the dowser falls.

6. Safety mechanism for motion picture projecting machines comprising a shaft, a dowser on the shaft, a notched disc on the shaft cooperating with a trigger for holding the dowser out of light obstructing position, an electromagnet, an armature for said magnet hingedly connected therewith and having a trip thereon, and means urging said armature away from said magnet and which, upon the deenergization of said magnet, operates the trip to strike the trigger and thereby release'the dowser to permit it to fall into light obstructing position.

1 7. Safety mechanism vfor motion picture projecting machines comprising a shaft, a dowser on the shaft, a notched disc on the shaft cooperating with a trigger for holding the dowser out of light obstructingposition, an electroinagnet, an armature for said magnet hingedly connected therewith and having atrip thereon, means urging said armature away from said magnet and which, upon the deenergization of saidmagnet, operates the trip to strike the .trigger and thereby release the dowser to permit it to fall into light obstructing position, electricaleontacts for closing the motorcircuit, and' means on the shaft adapted to open the electricalcontacts when the doWser falls. a

- =8. A safetydevice for motion picture projecting machines, including a dowser, means including a notched disc engaged by a triggerfor holding xthe dowser out of light ob structing position, an electromagnet, an armaturehinged 'on the magnet, spring means urging said armature away from said magnet, and atrip secured to-the armature and adapted to StIikGut-hG dowser holding means to release the. same when the armature isgpulled away from said magnetby said springmea-ns.

[In testimony whereof We have signed our names to this s ecification.

- J HN FRANCIS ADAMS.

THOMAS T8. ALLEN. 

